fix(33): match Revert AI Changes button to app styling

Replace amber colored button with neutral-400/800 style matching
all other header buttons.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/Header.tsx

@@ -371,7 +371,7 @@ export function Header() {
           {previousWorkflowSnapshot && (
             <button
               onClick={handleRevertAIChanges}
-              className="px-2.5 py-1 text-xs font-medium text-amber-300 bg-amber-500/15 hover:bg-amber-500/25 border border-amber-500/30 rounded transition-colors"
+              className="px-2.5 py-1.5 text-xs text-neutral-400 hover:text-neutral-200 hover:bg-neutral-800 rounded transition-colors"
               title="Restore workflow from before AI changes"
             >
               Revert AI Changes